"Physical Properties of Polymer-Based Nanocomposites"
Speaker: Professor Mircea Chipara, University of Texas Pan American, USA
1. Definition and examples of polymer-based nanocomposites
2. Synthesis of polymer-based nanocomposites (melt mixing and exfoliation, sonication, high pressure homogenization, in situ polymerization). Dispersion versus aggregation in polymer-based nanocomposites.
3. Phase transitions in polymers and block copolymers (glass transition, melting and crystallization transitions). The effect of the nanofiller on phase transitions (glass, melting, and crystallization temperatures).
4. Morphology/structural features of polymer-based nanocomposites. Surface areas and interfaces. Wetting of polymers to surfaces and nanoparticles. Adhesion and delamination in polymer-based nanocomposites.
5. The effect of nanofillers on the self-assembly capabilities of block copolymers.
6. Why nanocomposites? (a brief critical analysis on the advantages of polymer-based nanocomposites over polymer composites).
7. Future of polymer-based nanocomposites (new materials, biological features, and medical concerns)
“Nanoelectronic Transport: Quantum Engineering of Low-Dimensional Nanoensemble ”
Speaker: Professor VIJAY K. ARORA, Wilkes University, USA
Quantum (digital-type) concepts are gaining prominence over and above the classical (analog-type) ones in miniaturized devices where nanometer size can be less than or equal to the de Broglie wavelength of an electron in any of the three cartesian directions. An electric field driving electrons in these devices can be extremely high. This converts random carrier motion to a streamlined one, thereby limiting the velocity to thermal velocity or Fermi velocity depending on the degeneracy of the sample. This re-organization of the carrier velocities makes familiar Ohm’s law invalid, thereby enhancing the role of high-field velocity saturation in performance evaluation and characterization of nanostructures. This is based on the extreme nonequilibrium Arora distribution function developed by the presenter. Further, a free flight of a carrier may be interrupted by an emission of a quantum of energy in the form of a phonon or photon. This emission further limits the saturation velocity and also degrades the diffusion coefficient. The series of lectures will demonstrate that a higher mobility does not necessarily lead to a higher saturation velocity that is ballistic and scattering-independent, showing poor correlation with mobility-limiting scattering mechanisms. Ballistic transport where the channel length is below the scattering-limited mean free path has interesting connotations for mobility as mobility degrades in contradiction to the normally held view that elimination of scattering should result in its enhancement. This brings a new current-voltage relationship with resistance (both direct and incremental) rising with the applied dc voltage and reaching a resistance quantum in a nanowire, containing a very few electrons. A review of quantum-mechanical and high-field effects that have impact on the design of optoelectronic devices and other micro-circuits is presented. Applications to nanolayers, nanowires, graphene, and carbon nanotubes will be discussed.